The Greenpeace balloon

The Greenpeace balloon can carry three people - a pilot and two passengers, such as a campaigner and photographer or parachutist. Three more people are needed to form the ground crew.

Origin

The balloon can only be launched in low winds (up to 10 knots). In many parts of the world, this means it can only be flown two hours after sunrise and two hours before sunset.

This is because during the day the sun heats up the atmosphere and creates thermals that make balloon flying dangerous. In winter months, when the sun's heat is less powerful, there is a better chance of making daytime flights.

The balloon can stay airborne for a maximum of two hours in normal conditions (a cool temperature under 2000 metres above sea level).

There are two types of balloon flight - free or tethered.

During free flights, once launched the balloon is carried in the general direction of the wind.

The pilot can steer the balloon to an extent by taking advantage of different wind directions at higher and lower altitudes.

For tethered flights the wind speed must be less than for free flights (about 8 knots maximum), because the balloon is in effect resisting the wind and the hot air could be blown out of it, causing it to sink rapidly.

History

Historic Greenpeace balloon flights include flights over the Berlin wall in 1983, over the US Nevada nuclear test site in 1987 and over the Taj Mahal during the nuclear testing protest in India in 1998.

Actions

Greenpeace uses balloons for a variety of campaign purposes, such as for hanging banners, taking pictures of environmental crimes and measurements of airborne pollution from and as a platform for parachute jumps.